Multiple current-carrying capacity fuse and adaptor



June 1966 J. J. GALLAGHER ETAL 3,

MULTIPLE CURRENT-CARRYING CAPACITY FUSE AND ADAPTOR 2 Sheets-Sheet 1 Filed Oct. 5. 1963 1 u u n Jame: 6 2 //15A1r- J04.

I NVEN TOR S ATTORNEY June 21, 1966 J J, GALLAGHER ETAL 3,257,525

MULTIPLE CURRENT-CARRYING CAPACITY FUSE AND ADAPTOR Filed Oct. 5. 1963 2 Sheets-Sheet 2 JAMES J GALLAGHEg JOHN U GALLAGHE IN VENTORS ATTORNEY United States Patent 3,257,525 MULTIPLE CURRENT-CARRYIN G CAPACITY FUSE AND ADAPTOR James J. Gallagher, 5906 Mentana St., Hyattsville, Md., and John J. Gallagher, 5911 Anniston Road, Bethesda,

Filed Oct. 3, 1963, Ser. No. 313,619 2 Claims. (Cl. 200-419) latlons now in use, such as those in domestic housing,

industrial buildings and the like, incorporate several different capacity circuits according to requirements imposed on the particular circuit. For instance in the normal domestic household, lighting and appliance circuits are generally rated at or amps. Whereas circuits supplying electric Water heaters, driers and the like are generally rated at amps. This situation finds a parallel in industrial uses where circuits vary according to the loads expected to be imposed on them. The present art method of fusing a circuit theerfore imposes a requirement on the user to stock fuses of capacities equivalent to the number of circuits existing in the installation where they are to be used. As a result of the present system, disadvantages varying from mere inconvenience for the average householderto great expense in duplicate inventory and stock control for industrial users exist.

A further disadvantage resulting from the present fusing system results from the fact that the fuses are, in general, interchangeable, regardless of capacity, be tween receptacles of the same style fuse. This creates a serious safety problem since, through inadvertence or design, the fuses may be interchanged, regardless of clrcuits capacity, and overfusing of the circuit, with the attendant danger of fire and equipment damage, may result.

It is an object of the invention to provide a device for fusing electrical circuits which incorporates a multiple capacity fuse unit suitable for use in a number of different capacity circuits, the fusing capacity for particular circuit being determined by proper selection of the fuse receptacle.

It is a further object of this invention to provide a selectable fusing device in which the circuit-carrying capacity of the fusing'unit is permanently preselected according to the current-carrying capacity of the electrical circuit fused.

It is another object of this invention to provide fuse receptacles, which, in combination with a multiple current capacity fuse, have provision for easy initial adjustment thereof to limit the current-carrying capacity of an electrical circuit to a desired value.

It is yet another. object of this invention to provide a device which prevents the overfusing of an electrical circuit.

It is still another object of this invention to provide a device which simply converts the standard-type fusing system to a preselectable current-carrying capacity system.

It is still a further object of this invention to provide an electrical fusing system whereby the current limitation of a fuse circuit is determined by the configuration of the fuse receptacle.

It is a further object of this invention to provide an electrical fusing device which can be used indiscriminately in circuits of different capacities thereby reducing the size of fuse inventories required.

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This invention provides a multiple capacity fuse and receptacle combination suitable for use in circuits of different current capacities, the receptacle having provision for permanent preselection of the desired capacity of the fuse at the time of installation of the device.

The device consists of a fuse containing multiple fusing elements of different capacity which are mutually connected to a single contact at one of their ends and individually connected to individual-spaced contact terminals at their other ends. The receptacle comprises an insulating shell inside the usual fuse-receiving conductor which incorporates means to dispose a conductor between the conducting receptacle and the received portion of the fuse in such a way as to provide contact With a desired contact terminal of the multi-capacity fuse, when it is properly inserted in the receptacle.

The features and operation of this invention as well as other objects and many of the attendant advantages are more fully set out in the following detailed description when considered in connection with the accompanying.

, FIG. 5 is a side elevation view of the adaptor of FIG.

FIG. 6 is a side elevation view in section of the fuse of FIG. 2;

FIG. 7 is a top view in section of the fuse of FIG. 2;

FIG. 8 is a side elevation in section of another style fuse and receptacle incorporating an embodiment of this invention;

FIG. 9 is a perspective view of the fuse of FIG. 8 showing a variation in the receptacle thereof.

Referring now to FIG. 1 of the drawings for more complete understanding of the invention, a plug-type fuse receptacle is shown having usual block 1 of suitable insulating material. The block is provided with contacts 2 and 3 for connection to wiring the electrical circuit in the'usual manner. The fuse socket 4 consists of threaded insulating liner 6 having a conducting jacket 7 for-med around its outer surface. The socket is connected to receptacle block by contact screw 8 which also provides connection with contact 2 through conductor 9 in the usual fashion. Conducting jacket 7 contacts conductor 11 providing connection with contact 3. Socket 4 is provided, in this embodiment of the invention, with a slug conductor 12 fixed to jacket 7 and extending through liner 6 in such a way as to be exposed on the crest and lower side of .a portion of thread 13.

Referring now to FIGURES 2, 6 and 7, a plug-type fuse, adapted to co-operate with receptacle shown in FIG. 1, is illustrated. The fuse comprises a fuse body 14 of suitable electric insulating material, having a portion 16 adapted to fit within the receptacle and a shoulder 17 similar to standard plug fuse in present use. Contact member 18 is disposed at the bottom end of the fuse and extends upwardly coaxial with the axis thereof. Body portion 14 is provided with screw threads 19 in the walls thereof. Contact members 21 are provided at axiallyspaced intervals along screw thread 19. The threads illustrated in this embodiment of the invention are of the type known as acme threads and are generally characterized by a flat crest, slope sides and a fiat root. The contacts 21 are so positioned and so shaped as to comprise the portions of the thread known as the upperface and root of the segment where they are located. The shape of threads 19 and the disposition of contacts 21 form a preferred configuration since a tight, positive contact between the mating contact and slug 12 is insured since the thrust force realized when the fuse is tightly threaded into the socket will aid the mating contact. of course any other configuration offering similar advantages may be used.

Contact member 18 extends into the body of the fuse and are connected to fuse element 22 which is comprised, in this embodiment, of four radial segments, each having a notch 23 of differing size to provide diiferent currentcarrying capacities for each segment according to remaining cross-sectional area thereof. Contact members 21 extend into the fuse body connecting with appropriate segments of the fuse element 22. The fuse may include also the usual transparent disc 24 at the outer end which is held in place by cover 26 as shown. Fuse element 22 is connected at the center portion thereof to the portion of contact 18 extending into the body of the fuse.

Referring now to FIG. 3 of the drawings, fuse body 14 is shown fully threaded into fuse socket 4. Contact member 18 is shown engaged with contact screw 8. Slug conductor 12 has engaged one of the contact members 21 providing a complete circuit for contact 2v through con-- ductor 9 and contact screw 8 to contact member 18 and one of the fuse element segments 21 to contact 3 through conducting jacket 7 and conductor 11. Since the disposition of the contact members 21 Will be identical for all fuses embodying this invention, the location of slug conductor 12 will incorporate the same fuse element segment in the circuit for any fuse of this type inserted into the socket thereby fixing the current-carrying capacity of the circuit at the preselected value. It is intended that the embodiment will be furnished as a prefabricated unit and may be used as an original installation or a replacement for existing installations. The sockets may be selected by the installer according to an indicated current-carrying capacity for the socket as determined by the respective location of the slug conductor for that socket. The socket may bear suitable current-carry capacity indication in a similar fashion to that of the presently used fuse.

In instances where this device is to be incorporated into old installations, the variation of FIGS. 4 and is provided to allow adaptation of the standard Edison-type fuse socket. The adaptor consists of an insulator sleeve 27 having external threads 28 adapted to co-operate with the internal threads of the standard Edison-type socket, and internal threads 29 adapted to co-operate with the fuse structure of FIG. 2. Sleeve 27 is provided wih rectangular holes 31 radially disposed through the Walls thereof and axially spaced along the length of the sleeve. Conducting slug 32, adapted to co-operate with holes 31, is shown disposed through one of the holes in such a manner as to provide a conducting path through sleeve 27. It is contemplated that the walls of hole 31 will be formed with an inward taper and, similarly, slug 32 will have alike taper to co-operate therewith to provide a stop means to radially locate the slug in the sleeve wall. FIG. 5 shows the exterior of the adapator with slug 32 located in the next succeeding lower hole 31. Slug 32 may be provided with a pointed projection 33 disposed to engage the thread of the Edison-type fuse socket into which it is inserted and prevent removal of the adaptor unit once it has been inserted therein. Collar 34 is provided to prevent the adaptor unit from being threaded too deeply into the fuse socket. Of course the adjustable feature of the adaptor may be used in the replacement socket of FIG. 1 or the fixed feature of FIG. 1 may be used in the adaptor without varying. the scope of the invent-ion. Where the adjustable feature is furnished suitable markings may be placed adjacent to each hole 31 to indicate 4- the current capacity furnished by locating slug 32 at that point.

With reference now to FIG. 8 of the drawings, the features of the invention are shown embodied in a cartridge-type fuse. The fuse consists of a body 34, of usual form, having a conducting cap 36 thereon. The other end of body 34 is provided with threaded portion 37, adapted to engage the internal threads of cap 38. Cap 38 consists of inner insulator shell 39 which carries the internal threads of the cap and a conducting cap 41 surrounding the shell. Conducting slug 42 is disposed through shell 39 electrically connecting cap 41 to an interior portion of the thread. Body 34 is provided with a plurality of fuse elements 43 of different current-carrying capacity which are connected to link 44 at one end thereof, link 44, in turn, being connected to conducting cap 36. Elements 43 are connected at their other ends to contact members 44 disposed in axially spaced relationship through the walls of body 34. Threads 46 are preferably of the acme type and furnish the same contact mating benefits as outlined above for the plug fuse embodiment. Contact members 44 and conducting slug 42 are disposed through the thread elements in a manner similar to those described for the plug-type fuse embodiment of the invention and co-operate in a similar manner to provide positive contact therebetween.-

In operation then, this embodiment incorporates a permanent cap 38 furnished with the circuit to be fused. The replaceable fusing portion of the device consists of body 34 and the connected parts which are furnished as a unit and, when the fuse for a particular circuit requires replacing, is threaded into the cap 38 furnished with that circuit. Location of conducting slug 42, as in the plug fuse embodiment of the invention, determines the capacity of the fuse.

A further variation of this embodiment of FIG. 8 is shown in FIG. 9 where fuse body 34 is shown prior to assembly with cap 38. In this variation, the cap 38 is swivelly connected to terminal 47 of an electrical circuit. A second terminal 48 of the usual form is engageable with conducting cap 36 at the other end of fuse body 34.

This variation provides a permanently afiixed current capacity selector for an electrical circuit and prevents intel-changing of the selecting cap 38 between circuits. In operation the cap 38 is tilted upwardly and body 34 is threaded therein. The assembly is swiveled downwardly until cap 36 connects with terminal 48. The spacing between terminals 48 and 47 may be so arranged that cap 36 will not make contact with terminal 48 until the body 34 is fully threaded into cap 38. It is also contemplated that, with suitable structure well .known in the art, elements 43 could be made removable from body 34, producing a replaceable element, multi-capacity fuse system.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than is specifically described.

What is claimed as nev and desired to be secured by Letters Patent of the United States is:

1. A multiple capacity fuse system comprising: a fuse receptacle, and a fuse Iemovably threaded into said receptacle, a plurality of fuse elements of different current-carrying capacity in said fuse, means to connect one end of said elements to one side of an electrical circuit, said fuse having a dielectric threaded portion thereon, a plurality of electrical contacts disposed in spaced relationship through the threaded portion of said fuse, said elements being connected at the other ends thereof to individual ones of said contacts; at least the wall portion of said receptacle being con nected to the other side of said electrical circuit, a dielectric shell mounted in said receptacle, said shell having threads adapted to co-operate with the threads on said fuse, an electrical conductor disposed through said shell and in contact with the wall portion of said receptacle, said conductor disposed to contact one of said electrical contacts when said fuse is fully threaded into said receptacle.

and disposed to electrically connect with the contact of said receptacle when said fuse is fully threaded therein, and a plurality of fuse elements of different current-carrying capacities connected to said last mentioned cont-act at one of the ends thereof, Wall contacts disposed through said fuse in axially spaced relationship to one another, said elements being individually connected at their other ends to said Wall contacts, said wall contacts disposed to be adjacent to said apertures when said fuse is fully threaded in said receptacle.

2. A multiple capacity fuse assembly comprising:

a fuse receptacle, and a fuse removably threaded into said receptacle,

said receptacle having a threaded dielectric tubular Wall 10 portion therein, said wall portion having internal threads disposed thereon, said Wall portion further having a plurality of apertures therethrough, said apertures being disposed in axially spaced relationship at points intermediate the ends of said wall por- 15 References Cited by the Examiner UNITED STATES PATENTS tion, an electrical conductor slu-g disposed through ggg fi n one of said apertures, an electrical contact coaxially 2,791,661 5/1957 Taylor 200*119 disposed at the base of said receptacle;

said fuse comprising a cylindrical fuse body, said body having external threads thereon adapted to cooperate with the threads of said Wall portion, an electrical contact coaxially disposed at the base of said body 0 BERNARD A. GILHEANY, Primary Examiner.

H. B. GILSON, Assistant Examiner. 

1. A MULTIPLE CAPACITY FUSE SYSTEM COMPRISING: A FUSE RECEPTACLE, AND A FUSE REMOVABLY THREADED INTO SAID RECEPTACLE, A PLURALITY OF FUSE ELEMENTS DIFFERENT CURRENT-CARRYING CAPACITY IN SAID FUSE, MEANS TO CONNECT ONE END OF SAID ELEMENTS TO ONE SIE OF AN ELECTRICAL CIRCUIT, SAID FUSE HAVING A DIELECTRIC THREADED PORTION THEREON, A PLURALITY OF ELECTRICAL CONTACTS DISPOSED IN SPACED RELATIONSHIP THROUGH THE THREADED PORTION OF SAID FUSE, SAID ELEMENTS BEING CONNECTED AT THE OTHER ENDS THEREOF TO INDIVIDUAL ONES OF SAID CONTACTS; AT LEAST THE WALL PORTION OF SAID RECEPTACLE BEING CONNECTED TO THE OTHER SIDE OF SAID ELECTRICAL CIRCUIT, A DIELECTRIC SHELL MOUNTED IN SAID RECEPTACLE, SAID SHELL HAVING THREADS ADAPTED TO CO-OPERATE WITH THE THREADS ON SAID FUSE, AN ELECTRICAL CONDUCTOR DISPOSED THROUGH SAID SHELL AND IN CONTACT WITH THE WALL PORTION OF SAID RECEPTACLE, SAID CONDUCTOR DISPOSED TO CONTACT ONE OF SAID ELECTRICAL CONTACTS WHEN SAID FUSE IS FULLY THREADED INTO SAID RECEPTACLE. 